Towards a morphogenetic classification of eskers: Implications for modelling ice sheet hydrology

Perkins, Andrew J.; Brennand, Tracy A.; Burke, Matthew J.

doi:10.1016/j.quascirev.2015.12.015

Cited by 31 publications

(54 citation statements)

References 48 publications

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“…Sandy, cross-and ripple-laminated beds increase in frequency downstream, indicating a transition from high energy, episodic, sediment-laden, often hyperconcentrated flood flows to fully Newtonian flows with variable current strengths, typical of glaciofluvial environments (e.g., Brennand, 1994;Delaney, 2001aDelaney, , 2002. This morphology and sedimentology is characteristic of conduit fills (Brennand, 2000;Perkins et al, 2016), and these sediments are interpreted as such.…”

Section: Eskers and Kamesmentioning

confidence: 84%

Irish Ice Sheet dynamics during deglaciation of the central Irish Midlands: Evidence of ice streaming and surging from airborne LiDAR

2018

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High resolution digital terrain models (DTMs) generated from airborne LiDAR data and supplemented by field evidence are used to map glacial landform assemblages dating from the last glaciation (Midlandian glaciation; OI stages 2-3) in the central Irish Midlands. The DTMs reveal previously unrecognised low-amplitude landforms, including crevasse-squeeze ridges and megascale glacial lineations overprinted by conduit fills leading to ice-marginal subaqueous deposits. We interpret this landform assemblage as evidence for surging behaviour during ice recession. The data indicate that two separate phases of accelerated ice flow were followed by ice sheet stagnation during overall deglaciation. The second surge event was followed by a subglacial outburst flood, forming an intricate esker and crevasse-fill network. The data provide the first clear evidence that ice flow direction was eastward along the eastern watershed of the Shannon River basin, at odds with previous models, and raise the possibility that an ice stream existed in this area. Our work 2 demonstrates the potential for airborne LiDAR surveys to produce detailed paleoglaciological reconstructions and to enhance our understanding of complex palaeo-ice sheet dynamics.

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Section: Eskers and Kamesmentioning

confidence: 84%

Irish Ice Sheet dynamics during deglaciation of the central Irish Midlands: Evidence of ice streaming and surging from airborne LiDAR

2018

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“…The largest eskers are mostly sharp-crested (Figs. 12, 13), which may suggest that they formed in tunnels close to or at the ice surface (Perkins et al 2016).…”

Section: Laterallymentioning

confidence: 99%

“…-Eskers are categorised based on their cross-section geometry into sharpcrested, round-crested and flat-topped features (cf. Price 1973;Shreve 1985;Burke et al 2012bBurke et al , 2015Perkins et al 2016). In the proximal part of the system, a prominent (~10 m high, 30 m wide) single-ridge esker (5 in Fig.…”

Section: Glacial Geomorphology Of the Breiðamerkurjökull Esker Complexmentioning

confidence: 99%

“…The subsidiary eskers tend to be round-crested, indicating formation in subglacial positions (e.g. Price 1973;Perkins et al 2016). Flat-topped eskers form where channels transition from being under hydrostatic pressure to atmospheric pressure (Russell et al 2001), and/or where drainage enters standing water (e.g.…”

Section: Laterallymentioning

confidence: 99%

“…Punkari 1997;Brennand 2000;Boulton et al 2009;Storrar et al 2014a). Variations in esker cross-sectional geometry have been related to the geometry of the parent channel (Price 1973), as well as to the type of channel, mode of deposition and modification during ice melt-out (Perkins et al 2016). Sharp-crested eskers have been inferred to reflect deposition in level or descending terrain (Shreve 1985), or deposition and subsequent let-down in supraglacial channels (Price 1966;Syverson et al 1994;Perkins et al 2016).…”

Section: Wider Implications For Esker Formationmentioning

confidence: 99%

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Equifinality and preservation potential of complex eskers

Storrar

Ewertowski

Barr

et al. 2019

Boreas

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Eskers are useful for reconstructing meltwater drainage systems of glaciers and ice sheets. However, our process understanding of eskers suffers from a disconnect between sporadic detailed morpho-sedimentary investigations of abundant largescale ancient esker systems, and a small number of modern analogues where esker formation has been observed. This paper presents the results of detailed field and high-resolution remote sensing studies into two esker systems that have recently emerged at Hørbyebreen, Svalbard, and one at Breiðamerkurjökull, Iceland. Despite the different glaciological settings (polythermal valley glacier versus active temperate piedmont lobe), in all cases a distinctive planform morphology has developed, where ridges are orientated in two dominant directions corresponding to the direction of ice flow and the shape of the ice margin. These two orientations in combination form a cross-cutting and locally rectilinear pattern. One set of ridges at Hørbyebreen is a hybrid of eskers and geometric ridges formed during a surge and/or jökulhlaup event. The other sets of ridges are eskers formed time-transgressively at a retreating ice margin. The similar morphology of esker complexes formed in different ways on both glacier forelands implies equifinality, meaning that care should be taken when interpreting Quaternary esker patterns. The eskers at Hørbyebreen contain substantial ice cores with a high ice:sediment ratio, suggesting that they would be unlikely to survive after ice melt. The Breiðamerkurjökull eskers emerged from terrain characterised by buried ice which has melted out. Our observations lead us to conclude that eskers may reflect a wide range of processes at dynamic ice margins, including significant paraglacial adjustments. This work, as well as previous studies, confirm that constraints on esker morphology include: topographic setting (e.g. confined valley or broad plain); sediment and meltwater availability (including surges and jökulhlaups); position of formation (supraglacial, englacial or subglacial); and ice-marginal dynamics such as channel abandonment, the formation of outwash heads or the burial and/or exhumation of dead ice.

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Recent Basal Melting of a Mid‐Latitude Glacier on Mars

et al. 2017

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Evidence for past basal melting of young (late Amazonian‐aged), debris‐covered glaciers in Mars' mid‐latitudes is extremely rare. Thus, it is widely thought that these viscous flow features (VFFs) have been perennially frozen to their beds. We identify an instance of recent, localized wet‐based mid‐latitude glaciation, evidenced by a candidate esker emerging from a VFF in a tectonic rift in Tempe Terra. Eskers are sedimentary ridges deposited in ice‐walled meltwater conduits and are indicative of glacial melting. We compare the candidate esker to terrestrial analogues, present a geomorphic map of landforms in the rift, and develop a landsystem model to explain their formation. We propose that the candidate esker formed during a transient phase of wet‐based glaciation. We then consider the similarity between the geologic setting of the new candidate esker and that of the only other candidate esker to be identified in association with an existing mid‐latitude VFF; both are within tectonic graben/rifts proximal to volcanic provinces. Finally, we calculate potential basal temperatures for a range of VFF thicknesses, driving stresses, mean annual surface temperatures, and geothermal heat fluxes, which unlike previous studies, include the possible role of internal strain heating. Strain heating can form an important additional heat source, especially in flow convergence zones, or where ice is warmer due to elevated surface temperatures or geothermal heat flux. Elevated geothermal heat flux within rifts, perhaps combined with locally‐elevated strain heating, may have permitted wet‐based glaciation during the late Amazonian, when cold climates precluded more extensive wet‐based glaciation on Mars.

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Towards a morphogenetic classification of eskers: Implications for modelling ice sheet hydrology

Cited by 31 publications

References 48 publications

Irish Ice Sheet dynamics during deglaciation of the central Irish Midlands: Evidence of ice streaming and surging from airborne LiDAR

Irish Ice Sheet dynamics during deglaciation of the central Irish Midlands: Evidence of ice streaming and surging from airborne LiDAR

Equifinality and preservation potential of complex eskers

Recent Basal Melting of a Mid‐Latitude Glacier on Mars

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